I was wondering if there is a way to access the stereo parallax settings in the xrHelpers. Thanks!
Hi!
I am sorry, but I am not quite sure what you mean. I will try answers broadly, and I hope to “shoot in the right direction” with my answer 
The WebXR views (which are the “cameras” that are showing the scene) are defined by webxr itself. We get the information from the host (a browser, probably), and use this information to initialize a simple target camera that updates on each frame with a new transformation. The projection matrix is also being provided by webxr and should not be changed by the developer. it CAN be changed, but there is no guaranty that it will look as you expect it to be.
When initializing a new XR scene you can change the expected basic details such as camera’s fov, min and max Z, and that in turn will be provided to the WebXR host that will generate the correct matrices for us to use. This is the only time where it is ok to play with the eye definitions.
Does it make sense, or am I totally off?
Yes, it does. By parallax I mean the distance between left and right views. I seem to remember when I looked at WebVR API directly this was a configurable thing.
used to be, now it is set by webxr itself